U.S. Pat. No. 4,945,327 entitled "Molded Case Circuit Breaker Variable Arc Exhaust Shield" describes a so-called "current-limiting" circuit breaker wherein the contacts become electrodynamically repulsed upon intense overcurrent conditions to separate the contacts and generate an electric arc independent of the circuit breaker operating mechanism. An arc chute cools and quenches the arc to complete the circuit interruption process. The rapid acceleration provided by the contact arm arrangement allows the circuit to be interrupted in the early stages of the current waveform without requiring a slot motor for added acceleration to the contact arms. The arc chute includes a contact arm damper in the form of a silicone compound arranged at the top of the arc chute intermediate the interior surface of the circuit breaker cover and the topmost arc plate within the arc chute.
U.S. patent application Ser. No. 558,909 filed July 27, 1990 entitled "Molded Case Circuit Interrupter Trip Indicating Handle" includes a slidably mounted handle shutter that cooperates with the operating handle to prevent the arc exhaust gases that occur when the circuit breaker contacts are separated under overcurrent conditions from passing out through the circuit breaker handle access slot. In order for the handle shutter to travel freely within the circuit breaker cover, a part of the interior surface of the circuit breaker cover is removed to provide a shutter clearance shelf. The provision of such a clearance shelf within the interior surface of a molded plastic circuit breaker cover is extremely difficult to form integrally within the interior surface of the circuit breaker cover.
One purpose of the invention accordingly is to provide an insert to the interior surface of a molded plastic circuit breaker cover to define a recess for clearance of the circuit breaker operating handle shutter as well as to trap the circuit breaker arc chute between the interior of the cover and the bottom of the circuit breaker case when the cover is later fixedly attached to the case.